1. Field of the Invention
The present invention relates to a navigation method in which navigation data concerning a route from a current position of a moving body to a destination is transmitted from a navigation center to the moving body, and then route guidance is carried out at the moving body using the received navigation data. The present invention also relates to a navigation system and an information communications apparatus used in the navigation system.
2. Description of the Prior Art
One example of a navigation system in which a moving body such as a vehicle is provided with route/guidance data (i.e., route data and guidance data concerning searched recommended route) from a navigation center is disclosed in Japanese Laid-Open Patent Publication No. HEI 10-19588. In such a navigation system, map images and recommended route data (or the best route data) required for guiding a vehicle to a destination is transmitted from a navigation center (navigation base) to the vehicle. In particular, data communications are carried out between a data transmission system in the navigation center and the navigation apparatus in the vehicle. In this regard, the data transmission system includes a database which stores data required for guiding the vehicle to a destination.
Further, based on a request received from the navigation apparatus mounted on the vehicle, the data transmission system reads out required data from the database and creates map images. Furthermore, the data transmission system carries out a route search to produce optimum route data. Data indicating the created map images and the optimum route is transmitted from the data transmission system to the navigation apparatus. Then, based on the map images and optimum route data transmitted from the data transmission system, the navigation apparatus on the vehicle displays predetermined images on a display.
Further, Japanese Laid-Open Patent Publication No. HEI 8-33437 discloses a vehicle-mounted route guidance apparatus in which a new recommended route is transmitted from a control center to the vehicle-mounted route guidance apparatus when the vehicle strays from the original recommended route due to a driving operation error. In this arrangement, the vehicle-mounted route guidance apparatus transmits departure point data and destination data to the control center when necessary, and the control center transmits recommended route data to the vehicle-mounted route guidance apparatus.
Further, the vehicle-mounted route guidance apparatus is constructed to carry out judgements as to whether or not t h e vehicle is traveling along the recommended route. In the case where a judgement that the vehicle has strayed from the recommended route is made, the vehicle-mounted route guidance apparatus reestablishes the departure point and then transmits data of such new departure point and the destination to the control center. In this case, the control center searches a new recommended route to the destination based on the newly established departure point data and the destination data received from the vehicle-mounted route guidance apparatus, and then transmits such searched recommended route data to the vehicle-mounted route guidance apparatus.
However, in the prior art navigation systems described above, when data related to the recommended route is transmitted to the vehicle, the navigation center transmits all the data in a single communication operation. Consequently, in the case where the road conditions of the recommended route along which the vehicle is scheduled to travel change (e.g., due to traffic congestion caused by an accident) after all the data related to the recommended route has been received by the vehicle but before reaching destination, it is no longer possible to continue (or carry out) smooth route guidance based on (or using) the received route/guidance data for the recommended route.
Further, in the conventional navigation system, all of the route/guidance data from the departure point to the destination are transmitted to the vehicle. Therefore, the amount of the data to be transmitted becomes huge, so that it takes a long time to transmit the data and further it is necessary for the vehicle to temporally store the huge amount of the transmitted data. Further, such a long data transmission time not only increases communication cost at the user but also lengthens the time required for processing the data. In particular, when the distance between the departure point and the destination is long, such increases in the communication time and communication cost cannot be ignored or disregarded.
Furthermore, in the case where the vehicle is traveling in tunnels or mountain areas where radio waves can not reach weak radio or wave areas such as building shadows, it becomes impossible to carry out communications satisfactorily between the navigation center and the vehicle. As a result, there is a probability that the vehicle will not be able to obtain the required route/guidance data.
In view of the problems of the prior art described above, it is an object of the present invention to provide a navigation method, a navigation system and an information communications apparatus used in the navigation system in which it is possible to transmit navigation data extracted from the newest navigation information to a moving body from a navigation center over the entire time the moving body is traveling to the destination (instead of carrying out such transmission only at the time of departure of the moving body toward the destination).
In is another object of the present invention to provide a highly reliable navigation method, a navigation system and an information communications apparatus used in the navigation system in which it is possible to reliably transmit navigation data from the navigation center to the moving body regardless of communication conditions.
In order to achieve the above objects, the present invention is directed to a navigation method in which navigation data concerning a route from a current position of a moving body to a destination is transmitted from a navigation center to the moving body, and then route guidance is carried out at the moving body using the navigation data received from the navigation center, the method comprising the steps of:
(a) updating navigation information which includes various information concerning routes, the navigation information being stored in memory means provided in the navigation center;
(b) conducting a route search for setting a route from a current position of the moving body to a destination on the basis of the newest navigation information updated in the updating step (a);
(c) dividing the route set at the route searching step (b) into at least two portions;
(d) extracting navigation data concerning at least a head portion of the route divided at the dividing step (c) from said memory means storing the newest navigation information updated in the updating step (a);
(e) transmitting the navigation data extracted at the extracting step (d) from the navigation center to the moving body;
(f) conducting a route search for setting a route from a current position of the moving body to the destination on the basis of the newest navigation information updated in the updating step (a) after transmitting the navigation data for the head portion to the moving body but before transmitting navigation data for a remaining portion of the route;
(g) dividing the route set at the route searching step (f) into at least two portions;
(h) extracting navigation data concerning at least a head portion of the route divided at the dividing step (g) from said memory means storing the newest navigation information updated at the updating step (a); and
(i) transmitting the navigation data extracted at the extracting step (h) from the navigation center to the moving body.
According to the present invention described above, the determined route is divided into at least two portions, and then navigation data concerning the head portion of the divided route is transmitted from the navigation center to the moving body. Thus, as compared with the case where navigation data concerning all route from a departure point to a destination is transmitted to the moving body at one time, the amount of the navigation data to be transmitted to the moving body at one time is reduced. This allows the moving body to reliably receive the navigation data from the navigation center, and to smoothly begin route guidance.
Further, according to the present invention, the navigation information stored in the memory means is constantly updated. This allows the user of the moving body to obtain from the navigation center the navigation data extracted from the newest navigation information. Namely, according to the present invention, it becomes possible to provide the user with route guidance using the navigation data which is formed based on the newest navigation information that reflects various road conditions.
Furthermore, according to the present invention, a user of the moving body can always obtain from the navigation center navigation data extracted from the newest navigation information while the user is travelling on the route. Namely, this invention makes it possible to transmit navigation data extracted from the newest navigation information to the moving body from the navigation center over the entire time the moving body is traveling to the destination (instead of carrying out such transmission only at the time of departure of the moving body toward the destination).
In the present invention, it is preferred that the moving body transmits to the navigation center a request of the route search for setting the route from the current position of the moving body to the destination when reaching a predetermined request transmission point on the head portion whose navigation data has been received from the navigation center and along which the moving body is moving, and wherein the steps (f) to (i) are executed each time when the navigation center receives the request from the moving body.
According to the present invention described above, the moving body can obtain from the navigation center the navigation data extracted from the newest navigation information each time when the moving body reaches the predetermined request transmission points.
Further, in the present invention, it is also preferred that the navigation method further comprises the steps of:
making at least any one of a judgement as to whether or not the predetermined request transmission point on the head portion is positioned within a communications unable area or a poor communications area and a judgement as to whether or not a part of the head portion of the route where the moving body which has reached the request transmission point is expected to move until the moving body completely receives the navigation data for the head portion from the navigation center is partially or completely included in a communications unable area or a poor communications area; and
changing the request transmission point to other point in a case where it is judged at the judging step that the predetermined request transmission point on the head portion is positioned within the communications unable area or the poor communications area, or in a case where it is judged at the judging step that the part of the head portion of the route where the moving body which has reached the request transmission point is expected to move until the moving body completely receives the navigation data for the head portion from the navigation center is partially or completely included in the communications unable area or the poor communications area; wherein the judging step and the changing step is executed before the step (e) or (i).
According to the present invention described above, in the case where, for example, it is judged that the predetermined request transmission point is positioned within a tunnel, the request transmission point is changed to other point. This allows the navigation center to reliably receive the request from the moving body. Further, in the case where, for example, it is judged that the part of the head portion of the route where the moving body which has reached the request transmission point is expected to move until the moving body completely receives all of the navigation data for the head portion from the navigation center is partially included in a tunnel, the request transmission point is also changed to other point. This allows the moving body to reliably receive the navigation data from the navigation center.
Furthermore, in the present invention, it is also preferred that the step of changing the request transmission point is performed by increasing road length of the head portion. In this case, it is preferred that the division of the route at each of the steps (c) and (g) is carried out by dividing the route into a plurality of segments, wherein each of the portions of the route divided at the dividing step (c) or (g) is established using one or more of the segments as a unit, and wherein the step of changing the request transmission point is performed by increasing the road length of the head portion by at least one segment.
Moreover, in the present invention, it is also preferred that the step of changing the request transmission point is performed by decreasing road length of the head portion. In this case, it is preferred that the division of the route at each of the steps (c) and (g) is carried out by dividing the route into a plurality of segments, wherein each of the portions of the route divided at the dividing step (c) or (g) is established using one or more of the segments as a unit, and wherein the step of changing the request transmission point is performed by decreasing the road length of the head by at least one segment.
According to the present invention described above, the moving body can transmit the request to the navigation center from a point which is neither a communications unable area nor a poor communications area. This allows the navigation center to reliably receive the request from the moving body. Further, the moving body can receive the navigation data from the navigation center at an area which is neither a communications unable area nor a poor communications area. This allows the moving body to reliably receive the navigation data from the navigation center.
In the present invention, it is preferred that the navigation center detects that the moving body reaches a predetermined route search point on the head portion whose navigation data has been received from the navigation center and along which the moving body is moving, the navigation center automatically executes the steps (f)-(i), whereby the moving body receives from the navigation center navigation data for a remaining portion of the route.
According to the present invention described above, the moving body can obtain from the navigation center navigation data for a remaining portion of the route without transmitting to the navigation center a request of transmission for navigation data, when the moving body reaches the predetermined route search point.
In the present invention, it is preferred that when traffic situation or road condition of an untraveled route of the head portion is changed while the moving body is on the route corresponding to the head portion whose navigation data has been received from the navigation center, the steps (f)-(i) are executed.
According to the present invention described above, even if, for example, traffic congestion has occurred due to a car accident anywhere on an untraveled portion of the route where the moving body has not yet traveled, it is possible for the moving body to obtain from the navigation center navigation data concerning a route that enables the moving body to avoid such a traffic congestion.
Another aspect of the present invention is directed to a navigation system in which navigation data concerning a route from a current position of a moving body to a destination is transmitted from a navigation center to the moving body, and then route guidance is carried out at the moving body using the navigation data received from the navigation center, the system comprising:
memory means provided in the navigation center for storing navigation information which includes various information concerning routes;
updating means provided in the navigation center for updating the navigation information stored in said memory means;
route searching means provided in the navigation center for setting a route from a current position of the moving body to a destination on the basis of the newest navigation information stored in said memory means;
dividing means provided in the navigation center for dividing the route set by said route searching means into at least two portions;
extracting means provided in the navigation center for extracting navigation data concerning at least a head portion of the route divided by said dividing means from said memory means storing the newest navigation information updated by said updating means;
transmitting means provided in the navigation center for transmitting from the navigation center to the moving body the navigation data extracted by said extracting means;
control means provided in the navigation center for controlling each of said memory means, said updating means, said route searching means, said dividing means, said extracting means and said transmitting means; and
receiving means provided in the moving body for receiving the navigation data transmitted from said transmitting means of the navigation center, wherein said control means controls said route searching means to set a route from a current position of the moving body to the destination on the basis of the newest navigation information stored in said memory means, controls said dividing means to divide the route set by said route searching means into at least two portions, controls said extracting means to extract navigation data concerning at least a head portion of the route divided by said dividing means from said memory means storing the newest navigation information updated by said updating means, and then controls said transmitting means to transmit from the navigation center to the moving body the navigation data extracted by said extracting means, after transmitting the navigation data for the head portion to the moving body but before transmitting the navigation data for the route which is newly set by said rout searching means.
In this invention, it is preferred that the moving body transmits to the navigation center a request of the route search for setting the route from the current position of the moving body to the destination when reaching a predetermined request transmission point on the head portion whose navigation data has been received from the navigation center and along which the moving body is moving, and wherein said control means controls each of said route searching means, said dividing means, said extracting means and said transmitting means so that each means performs the respective processes, each time when the navigation center receives the request from the moving body.
Further, in this invention, it is also preferred that the navigation system further comprises:
judging means for making at least any one of a judgement as to whether or not the predetermined request transmission point on the head portion is positioned within a communications unable area or a poor communications area and a judgement as to whether or not a part of the head portion of the route where the moving body which has reached the request transmission point is expected to move until the moving body completely receives the navigation data for the head portion from the navigation center is partially or completely included in a communications unable area or a poor communications area; and
changing means for changing the request transmission point to other point in a case where it is judged by said judging means that the predetermined request transmission point on the head portion is positioned within the communications unable area or the poor communications area, or in a case where it is judged by said judging means that the part of the head portion of the route where the moving body which has reached the request transmission point is expected to move until the moving body completely receives the navigation data for the head portion from the navigation center is partially or completely included in the communications unable area or the poor communications area; wherein the judgement by said judging means and the change of the request transmission point by said changing means are executed before the navigation data is transmitted to the moving body via said transmission means.
Furthermore, in this invention, it is also preferred that the division of the route by said dividing means is carried out by dividing the route into a plurality of segments, wherein each of the portions of the route divided by said dividing means is established using one or more of the segments as a unit.
Moreover, in this invention, it is also preferred that the change of the request transmission point by said changing means is performed by increasing road length of the head portion by at least one segment.
Still further, in this invention, it is also preferred that the change of the request transmission point by said changing means is performed by decreasing road length of the head portion by at least one segment.
Still further, in this invention, it is also preferred that each segment is established so as to have the same number of bits. In this case, the change of the request transmission point by said changing means may be performed by increasing road length of the head portion by at least one segment. Further, the change of the request transmission point by said changing means may also be performed by decreasing road length of the head portion by at least one segment.
Still further, in this invention, it is also preferred that each segment is established so as to have a substantially uniform road length. In this case, the change of the request transmission point by said changing means may be performed by increasing road length of the head portion by at least one segment. Further, the change of the request transmission point by said changing means may also be performed by decreasing road length of the head portion by at least one segment.
In this invention, it is preferred that when the navigation center detects that the moving body reaches a predetermined route search point on the head portion whose navigation data has been received from the navigation center and along which the moving body is moving, said control means controls each of said route searching means, said dividing means, said extracting means and said transmitting means so that each means performs the respective processes, whereby the moving body receives from the navigation center navigation data for a remaining portion of the route.
In this invention, it is preferred that when traffic situation or road condition of an untraveled route of the head portion is changed while the moving body is on the route corresponding to the head portion whose navigation data has been received from the navigation center, said control means controls the route searching means to set a route from a current position of the moving body to the destination on the basis of the newest navigation information stored in said memory means, controls said dividing means to divide the route set by the route searching means into at least two portions, controls said extracting means to extract the navigation data concerning at least the head portion of the route divided by said dividing means from said memory means storing the newest navigation information updated by said updating means, and then controls said transmitting means to transmit from said transmitting means of the navigation center to the moving body the navigation data extracted by said extracting means.
Other aspect of the present invention is directed to an information communications apparatus used in a navigation system in which navigation data concerning a route from a current position of a moving body to a destination is transmitted from a navigation center including the information communications apparatus to the moving body, and then route guidance is carried out at the moving body using the navigation data received from the navigation center, the apparatus comprising:
memory means for storing navigation information which includes various information concerning routes;
updating means for updating the navigation information stored in said memory means;
route searching means for setting a route from a current position of the moving body to a destination on the basis of the newest navigation information stored in said memory means;
dividing means for dividing the route set by said route search means into at least two portions;
extracting means for extracting navigation data concerning at least a head portion of the route divided by said dividing means from the memory means storing the newest navigation information updated by said updating means;
transmitting means for transmitting the navigation data extracted by said extracting means from the navigation center to the moving body; and
control means for controlling each of said memory means, said updating means, said route searching means, said dividing means, said extracting means and said transmitting means,
wherein said control means controls the route searching means to set a route from a current position of the moving body to the destination on the basis of the newest navigation information stored in said memory means, controls said dividing means to divide the route set by said route search means into at least two portions, controls said extracting means to extract navigation data concerning at least a head portion of the route divided by said dividing means from the newest navigation information, and then controls said transmitting means to transmit from the navigation center to the moving body the navigation data extracted by said extracting means, after transmitting the navigation data for the head portion to the moving body but before transmitting the navigation data for the route which is newly set by said rout searching means.
Yet other aspect of the present invention is directed to a navigation method in which navigation data and guidance data concerning a route from a navigation starting point to a navigation ending point are divided at a navigation center and then transmitted from the navigation center to a moving body so that route guidance is carried out at the moving body using the data, the method comprising a step of carrying out a route search based on newest data and then extracting guidance data before the navigation center transmits the divided route data and guidance data to the moving body.
Yet other aspect of the present invention is directed to a navigation method in which navigation data and guidance data concerning a route from a navigation starting point to a navigation ending point are divided at a navigation center and then transmitted from the navigation center to a moving body so that route guidance is carried out at the moving body using the data, the method comprising a step of carrying out a route search based on newest data and then extracting guidance data each time when the navigation center receives from the moving body a request for transmission of the route data and the guidance data.
Yet other aspect of the present invention is directed to a navigation method in which navigation data and guidance data concerning a route from a navigation starting point to a navigation ending point are divided at a navigation center and then transmitted from the navigation center to a moving body so that route guidance is carried out at the moving body using the data, the method comprising a step of carrying out a route search based on newest data and then extracting guidance data each time when the navigation center transmits the divided route data and guidance data to the moving body.
The above described and other objects, structures and advantages of the present invention will be apparent when the following description of the preferred embodiment will be considered in conjunction with the appended drawings.